If they did did this putting Batman in the last episode would leave even more haters than Smallville had. I
Season 1) Bruce starts traveling the world to train (age 14-15)
Season 2) Bruce trains with a new master and solves mystery's around the city he lives in (age 16-18)
Season 3) Bruce becomes "Naito" a.k.a The Knight as he trains in japan (age 18-20)
Season 4) Bruce is “Hēi'àn qíshì” a.k.a "The Dark Knight" in China. (age 21-22)
Season 5-10) He returns to Gotham and is Batman! He fights his own rouge gallery.